Ethylene-vinyl alcohol copolymer (hereinafter referred to as “EVOH”), which is excellent in transparency, gas-barrier properties, solvent resistance, oil resistance, mechanical strength, and the like, is conventionally used as packaging materials, plastic molded articles, and protective-film forming materials for surfaces of metal, paper, and wood, and the like.
The followings are widely used as a method of forming an EVOH coating: melt extrusion, injection molding, and a method involving lamination of an EVOH film. Further, known is a method involving application of an EVOH solution followed by drying. According to the above method involving application of an EVOH solution, a thin film can easily be obtained, which can be formed even on a surface of a base material having a complicated shape.
However, in the method involving application of an EVOH solution, use of a highly concentrated EVOH solution is difficult due to the solubility issue. Moreover, the method faces challenges in terms of safety and economic efficiency. For example, work environments may deteriorate due to volatilization of an organic solvent, and thus an apparatus for collecting an organic solvent may be required.
Accordingly, technologies have been proposed in which EVOH is prepared in a form of an aqueous dispersion, and the aqueous dispersion of EVOH is then applied (for example, see Patent Documents 1 and 2). These technologies can solve the aforementioned challenges in terms of safety and economical efficiency.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. H05-86240
Patent Document 2: Japanese Unexamined Patent Application, Publication No. H05-93009